Diffusion timing mechanism

ABSTRACT

A timing device for controlling mechanical, electrical or chemical systems is provided which functions in response to controlled diffusion of solvent through an elastomer.

United States Patent 151 3,662,127 Gimler et al. 1 May 9, 1972 541 DIFFUSION TIMING MECHANISM 2,88l,285 4/1959 Bank ..20o/34x 3,156,792 l1 1964 1 [72] Inventors: John R. Glmler, Succasunna; Stephen E. Long 200/34 3,236,961 2/1966 Kappel ..200/34 Jurman, Ledgewood; Robert W. Schnet- 3 334 204 8 l9 7 "er, Wharton a of NJ. 6 Brenny et al ..200/34 X 2,879,892 3/1959 Frakes ..200/8l.9 X A gn Hercules Inc p r Wilming on, Del. 3,470,819 9/1969 Heinemann ..108/82 [22] Filed: Sept. 26, 1969 Primary Examiner-J. R. Scott PP N04 861,293 Attorney-Michael B. Keehan 52 U.S. c1. ..200/34,200/33, ZOO/81.9 ABSTRACT [51] Int.Cl ..H0lh 7/03, HOlh 43/00 A d f 58 Field ofSearch ..200/34 81.9 33-210/243- "l' l' elecmca' 314/99 28 100. 5 E 96 6 chemlcal systems 1s provlded wh1ch functlons 1n response to controlled diffusion of solvent through an elastomer. [5 6] References Cited 4 Claims, 3 Drawing Figures UNITED STATES PATENTS 2,866,862 12/1958 Bachi ..200/34 PATENTEDMM 91912 I 3,662,127

JOHN R. GIMLER STEPHEN E. JURMAN ROBERT W. SCHNETTLER INVENTORS ATTORNEY DIFFUSION TIMING MECHANISM This invention relates to a timing device suitable for initiating action of chemical, mechanical and electrical systems at a pre-established time as a result of controlled diffusion of solvent through an elastomer.

Timing devices employed for actuating systems of all types at predetermined times are well known. Most timing mechanisms function in response to mechanical or electrical action or a combination thereof. The timing device of this invention is unique in that it requires no external driving power and has no moving parts per se. The timing device of this invention is particularly suitable for use in applications where extremely high reliability is required but where high precision in the precise moment of initiation of actuation of the device or system to be controlled is of secondary importance.

Elastomers are known to swell in the presence of certain solvents. Utilizing this phenomena, the timing device of this invention functions through absorption of solvent by an elastomer, controlled diffusion of solvent through the elastomer, and evaporation of solvent from a surface of the elastomer through an orifice into an expansion area.

Broadly, the timing device of this invention comprises (a) a timing body having an internal chamber and an orifice, said orifice communicating the internal chamber to an expansion area, (b) an elastomer and a solvent diffusable through said elastomer being contained within the internal chambensaid elastomer being swelled with said solvent, said solvent-swelled elastomer being positioned within said internal chamber so as to cover the orifice in the timing body providing a permeable barrier between the orifice and the solvent, and (c) means responsive to diffusion of the solvent through the elastomer for controlling operation of a system.

The following drawings will more fully illustrate the diffusion timing mechanism of this invention.

FIG. 1 is a schematic drawing of a diffusion timing device of this invention illustrating use of the device to control the rate of change of inductance in an oscillator circuit.

FIG. 2 is a schematic drawing illustrating another embodiment of a diffusion timing device of this invention which is employed to energize an electrical circuit.

FIG. 3 is a segmented schematic drawing illustrating another embodiment of a diffusion timing device of this invention and particularly illustratinga means responsive to contraction of the solvent-swelled elastomer for releasinga liquid into a system.

In FIG. '1 a timing body 10 having an orifice l2 communicating the internal chamber 14 of timing body 10 to an expansion area 16 (not shown) is illustrated. The internal chamber 14 of timing body 10 contains a plug 18 of elastomeric material, shown in the swelled or expanded state, positioned at the base 20 of the internal chamber 14. The plug 18 covers the orifice 12 providing a barrier between the orifice 12, expansion area 16 and the solvent 22 which is in intimate contact with plug 18 and which is diffusible through plug 18. Solvent 22 causes plug 18 to swell within the internal chamber 14. A piston 24 floats on solvent 22 and is sealed from the solvent 22 with a water seal 23. One end of a connecting rod 26 is attached to piston 24. The opposite end of connecting rod 26 is comprised of a metallic core 28. The metallic core '28 is positioned directly above a current carrying coil 30 which is electrically connected to an oscillator circuit illustrated as box 32. In operation of the timing device solvent 22 slowly difiuses through elastomeric plug 18 and passes through orifice 12 into expansion area 16. Piston 24 is lowered within chamber-14in response to the controlled diffusion of solvent 22. The metallic core 28 of connecting rod 26 being integrally connected to piston 24 is also lowered and moves into the center of coil 30. The metallic core 28 passing through the magnetic field provided by coil30 continually changes the inductance of the oscillator circuit effectively controlling the system in response to diffusion of solvent through the timing device.

FIG. 2 illustrates another embodiment of the diffusion timing device of this invention. A cylindrical chamber body is prepared in two parts, a base 34 and a cap 36. The chamber base 34 contains an orifice 38 in bottom wall 40 and has electrical conductors 42 and 43 passing respectively through two insulators 44 and 45 inserted inholes 46 and 48 in the side walls of base 34. Electrical conductors 42 and 43 are connected to an electrical system to be controlled. Conductor 43 is connected to a conductive plate 50. One end of a small rod 52 of elastomeric material is secured by suitable means to conductive plate 50. A conductive cap 54 is secured at the other end of rod 52 opposite conductive plate 50. Conductive cap 54 is connected to electrical conductor lead 42. Conductive cap 54 has a longitudinal contact 56 extending toward conductive plate 50 and parallel with the longitudinal axis of rod 52 but shorter in length than rod 52. The bottom wall 40 of base 34 and chamber orifice 38 are covered with an elastomeric plug 58 illustrated in swelled condition. The chamber base 34 is filled with an electrically non-conductive solvent 60 which covers both the elastomeric plug 58 and rod 52. As solvent 60 diffuses through elastomeric plug 58 the level of solvent within the chamber base 34 is lowered until all the solvent 60 has diffused'through plug 58 and evaporated through orifice 38. After diffusion of solvent 60 is complete, rod 52 starts contracting to its original non-swelled size. Rod 52 is sized so that during contraction contact 56 touches conductive plate 50 energizing the circuit to be controlled.

In FIG. 3 timing body 62 is illustrated having a body cover and a base plate 66. The timing body (as assembled) has an inner chamber 68, and outer chambers 70 and 72. Inner chamber 68 and outer chambers 70 and 72 are communicatively connected through slots 74 and 76 respectively in interior walls78 and 80. An elastomeric ring 82 is positioned in the annular space defined between interior walls 78 and 80 and covers slots 74 and 76 communicating the inner and outer chambers. Elastomeric ring 82 also covers an orifice 84 which communicates the ring to the atmosphere. 7

Inner chamber 68 is filled with a liquid to be released through slots 74 and 76 into outer chambers 70 and 72. Outer chambers 70 and 72 initially contain a solvent diffusable through elastomeric ring 82. Outer chambers 70 and 72 also contain a series of scaled openings as represented by openings 86 in the base plate 66. These openings are sealed with a material which is non-reactive to the solvent diffusable through the elastomeric plug but which is reactive or soluble with the liquid to be released.

In operation of the timing device of FIG. 3, solvent contained in chambers 70 and 72 diffuses slowly through elastomeric ring 82 and is released to theatmosphere through orifice 84. After all the solvents have diffused through elastomeric ring 82 and evaporated through orifice 84 into the atmosphere, ring 82 contracts releasing liquid stored in chamber 68 through slots 74 and 76 into chambers 70 and 72. The released liquid reacts or dissolves the sealing material covering openings 86 in chambers 70 and 72 and is released into a desired system.

The preferred timing device of this invention functions in response to contraction of the solvent-swelled elastomer as illustrated in FIGS. 2 and 3 following diffusion of all solvent through theelastomer and substantially complete evaporation ofsolvent through the orifice into the expansion area. The presence of solvent vapors in contact with the elastomer will maintain the elastomer in its swelled condition. It is necessary only tomaintain the solvent at a temperature at which it is a liquid toensure diffusion of solvent through the elastomer. In the timing device of this invention the elastomeric plug in its expanded or swelled condition covers the orifice. The swelled elastomer thus functions as a permeable barrier to the expansionarea by which controlled diffusion of solvent is possible.

The elastomeric materials which can be employed in the timing device of this invention includeany material which will swell in contact with a solvent, will permit diffusion of the solvent through the elastomer and which substantially recovers its original size after the solvent is removed from contact with the elastomer. The elastomer-solvent combination chosen for a particular application will depend upon various factors such as the temperature at which the device will be used, and flammability and toxicity of the diffusion solvent. A particularly suitable and preferred elastomer-solvent combination having the properties of low toxicity, non-flammability and Compression defined as follows: v Elnstomer Expanded Diameter (free)Elastomer Diameter ln Timing Chamber Elnstomer Expanded Diameter(free) non-conductivity necessary in electrical applications is silicon 5 As is seen from the above data, the rate of diffusion and rubber and trichlorotrifiuoroethane (CCl FCClF evaporation of solvent through elastomer is very slow. Utiliz- Table I below is illustrative of some typical solventing the slow diffusion rate, timing mechanisms can be elastomer combinations which can be employed in the diffudesigned to provide periods of operability from hours to sion timing device of this invention. Linear swell of the months while maintaining the size of the overall device at a elastomers in certain solvents is given. minimum.

TABLE I.ELASTOMER/SOLVENT SYSTEMS [Percent linear swell in solvents at 75 F.]

' Solvents Trichloro- Carbon Methyl trifiuoro- Stoddard tetrachlo- Methylene chloro- Elastomers ethane solvent ride chloride form Neoprene W rubber 35 43 35 Buna N rubber... 11 52 24 Buna S rubber 28 31 26 44 Silicon polysiloxane rubber. 34 29 35 27 33 Butyl rubber 21 37 56 19 35 Natural rubber 17 50 44 34 59 The expansion area into which the solvent evaporates is preferably the atmosphere. However, closed expansion areas What I claim and desire to protect by Letters Patent is: 1. A timing device for controlling operation of a system at a can be provided as an integral part of the timing mechanism of pre-established time period, said timing device comprising:

this invention if the closed expansion area provides adequate volume to allow sufficient difiusion of the solvent into the expansion area whereby a means responsive to the diffusion of solvent through the elastomer can be made operative prior to the system pressure reaching equilibrium.

The time required for a solvent to diffuse through an elastomer and thus control the action of the timing device of this invention is dependent upon elastomer length and crosssectional area, the orifice size which determines the area of the elastomer exposed to the expansion area, the amount of compression on the elastomer in its swelled condition and the particular elastomer-solvent combination employed. Diffusion rate is increased by increasing the ratio of orifice size to elastomer cross-sectional area and is decreased by increasing the length of the elastomer. As the compression of the elastomer increases the diffusion rate of solvent through the elastomer decreases.

The effect of compression on diffusion rate through a rubber plug and evaporation therefrom is presented in Table II for a silicon plug 541 inch in diameter by M1 inch long (nonswelled dimensions) in contact with trichlorotrifluoroethane. Diffusion rate can be altered through control of the various parameters listed above.

a. a timing body having a first internal chamber, a second internal chamber, a conduit connecting said first and second internal chambers, and an orifice therethrough connecting said conduit to the atmosphere,

b. an elastomer member housed within said conduit,

c. a liquid solvent diffusable through said elastomer member contained within said first internal chamber, said liquid solvent expanding said elastomer to cover said orifice and seal said conduit connecting the first and second internal chambers,

d. a fluid contained within the second internal chamber, said fluid being released after said pre-established time period into said first chamber by contraction of the solvent expanded elastomer member after diffusion of the liquid solvent from the first internal chamber through the elastomer member and orifice into the atmosphere, and

. means in said first internal chamber responsive to the flow of said fluid from the second internal chamber into the first internal chamber for controlling operation of the system.

2. The timing device of claim 1 wherein the elastomer is silicon rubber and the solvent is trichlorotrifluoroethane.

3. The timing device of claim 1 wherein the elastomer is butyl rubber and the solvent is trichlorotrifluoroethane.

4. The timing device of claim 1 wherein the elastomer is natural rubber and the solvent is trichlorotrifluoroethane. 

1. A timing device for controlling operation of a system at a pre-established time period, said timing device comprising: a. a timing body having a first internal chamber, a second internal chamber, a conduit connecting said first and second internal chambers, and an orifice therethrough connecting said conduit to the atmosphere, b. an elastomer member housed within said conduit, c. a liquid solvent diffusable through said elastomer member contained within said first internal chamber, said liquid solvent expanding said elastomer to cover said orifice and seal said conduit connecting the first and second internal chambers, d. a fluid contained within the second internal chamber, said fluid being released after said pre-established time period into said first chamber by contraction of the solvent expanded elastomer member after diffusion of the liquid solvent from the first internal chamber through the elastomer member and orifice into the atmosphere, and e. means in said first internal chamber responsive to the flow of said fluid from the second internal chamber into the first internal chamber for controlling operation of the system.
 2. The timing device of claim 1 wherein the elastomer is silicon rubber and the solvent is trichlorotrifluoroethane.
 3. The timing device of claim 1 wherein the elastomer is butyl rubber and the solvent is trichlorotrifluoroethane.
 4. The timing device of claim 1 wherein the elastomer is natural rubber and the solvent is trichlorotrifluoroethane. 